Objective: To investigate the inhibitory effect of tormentic acid (TA) on the proliferation of rat hepatic stellate cell (HSC-T6) and transformation growth factor-β (TGF-β)/Smad signal pathway

so as to explore its anti-hepatic fibrosis mechanism. Method: Cell counting kit (CCK)-8 assay was used to observe the proliferation of HSC-T6 cell after treated with TA (0

50

60

70

80

90

100 μmol · L-1) for 24 h. The half inhibitory concentration (IC50) of TA was calculated

and the optimal concentration was selected. HSC-T6 cells in the logarithmic phase were collected and divided into normal control group

stimulation group

and high

middle and low-dose TA (40

20

10 μmol · L-1) treatment groups. Cell colony formation was observed using Giemsa staining; and cell apoptosis and cell cycle were examined by flow cytometry. The protein expression of Col-Ⅲ was detected by immunocytochemistry. Additionally

the protein expressions of Smad4 and α-SMA were detected by Western blot. Result: TA could inhibit the proliferation of HSC-T6 cells in a concentration-dependent manner

and its IC50 value was 81.7 μmol · L-1. Compared with the normal group

TA significantly inhibited the colony formation in a dose-dependent manner. Meanwhile

TA could also significantly promote HSC-T6 cell apoptosis and arrest cell cycle in G2 phase (P<0.05

P<0.01). In addition

TA obviously decreased the protein expressions of Col-Ⅲ

α-SMA and Smad4 (P<0.05). Conclusion: Tormentic acid can significantly suppress HSC-T6 cell activation. Its mechanism may be correlated with the promotion of cell apoptosis

the retardation of cell cycle and the inhibition of TGF-β/Smad pathway.